0A
Viessmann fault code
Viessmann 0A: CO limiter has responded (CO concentration too high), or gas pressure switch has responded (gas pressure too low)
Engineer only
Viessmann describes 0A on Vitodens 100-W (B1HC/B1KC) boilers as: cO limiter has responded (CO concentration too high), or gas pressure switch has responded (gas pressure too low).
What you can safely do
There is nothing you can safely do yourself with this one. Leave the boiler off and book an engineer.
Call a Gas Safe engineer if
- Book a Gas Safe registered engineer.
- If a carbon monoxide alarm is sounding, or anyone feels unwell (headache, dizziness, nausea), get fresh air, leave the boiler off and call 0800 111 999.
Find a Gas Safe engineer near you
Opens the official Gas Safe Register search.
Applies to: Vitodens 100-W (B1HC/B1KC). Codes can differ between models, so check your manual.